In his later work, Freud proposed that the human psyche could be divided into three parts: Id, ego and super-ego. Freud discussed this model in the 1920 essay Beyond the Pleasure Principle, and fully elaborated upon it in The Ego and the Id (1923), in which he developed it as an alternative to his previous topographic schema (i.e., conscious, unconscious and preconscious).

The id is the completely unconscious, impulsive, childlike portion of the psyche that operates on the "pleasure principle...